I just taught Lexi roll over! I used a technique like the previous poster's. I also have a problem with her jumping at the treat. I try to be firm, and if she jumps a few times, I put the treat away and try a little later.
I do sit. Down. (Treat to floor by nose)
Then while she is down, I take the treat that is by her nose and kind of circle it around her head. She follows it with her head, which causes her to roll over.
Of course, now when I try to teach her "paw", she rolls over instead!
